The present invention relates to a hot-blast stove for use in blast furnaces and of the type including a cylindrical metallic shaft casing which has a funnel-shaped widened portion joined to a metallic cupola of a larger diameter than the cylindrical casing, the refractory lining of the cupola being arranged independently of the refractory lining of the cylindrical shaft, which cylindrical shaft lining surrounds a combustion chamber and a grating chamber within the cylindrical shaft.
Hot-blast stoves of the above-mentioned type, i.e. so-called inner-shaft hot-blast stoves, are associated with a great number of technical problems in the area of transition between the shaft and the cupola, both with regard to the refractory linings and also with regard to the external pressure supporting plate metal casings or covers. Especially in hot-blast stoves of the type including an overlapping or projecting cupola, wherein the larger diameter cupola casing is joined to the shaft casing through a horizontal metal plate in the form of a step that supports the lining of the cupola, disadvantageous stress conditions result in the casing at the area of transition from the shaft to the cupola. On the one hand, the weight of the cupola lining is transmitted with a detrimental leverage through the horizontal plate or step to the metal casing. On the other hand, the stresses generated by the inner pressure of the hot blast stove (up to six atmospheres overpressure in modern installations) are directed through the horizontal plate or step, with the result of further extreme stressing of the metal casing. Additionally, due to relatively large temperature differences, which result from either damage to the lining during operation or atmospheric influences, there may be additional substantial stresses in the metal casing. All such stresses require a considerable expenditure for structural design and materials in order to provide reliable operation of the hot-blast stove.
Similar disadvantages are present in the hot-blast stove described in German specification DT-OS 2,003,039. Therein the cupola lining rests on brackets or consoles that are attached above a funnel-shaped widened portion widening on the metal casing, so that the weight of the lining likewise acts with a disadvantageous leverage on the metal casing. This disadvantage is amplified by the peak stresses generated through the attachment of the brackets to the metal casing.